Begin incorporating Python unit tests into build

We now build a separate APE binary for each test so they can run in
parallel. We've got 148 tests running fast and stable so far.

third_party/python/Lib/decimal.py

@@ -1,10 +1,51 @@
-# try:
-from _decimal import BasicContext, Clamped, Context, ConversionSyntax, Decimal, DecimalException, DecimalTuple, DefaultContext, DivisionByZero, DivisionImpossible, DivisionUndefined, ExtendedContext, FloatOperation, HAVE_THREADS, Inexact, InvalidContext, InvalidOperation, MAX_EMAX, MAX_PREC, MIN_EMIN, MIN_ETINY, Overflow, ROUND_05UP, ROUND_CEILING, ROUND_DOWN, ROUND_FLOOR, ROUND_HALF_DOWN, ROUND_HALF_EVEN, ROUND_HALF_UP, ROUND_UP, Rounded, Subnormal, Underflow, getcontext, localcontext, setcontext
-from _decimal import __doc__
-from _decimal import __version__
-from _decimal import __libmpdec_version__
-# except ImportError:
-#     from _pydecimal import *
-#     from _pydecimal import __doc__
-#     from _pydecimal import __version__
-#     from _pydecimal import __libmpdec_version__
+try:
+    from _decimal import *
+    from _decimal import __doc__
+    from _decimal import __version__
+    from _decimal import __libmpdec_version__
+except ImportError:
+    from _pydecimal import *
+    from _pydecimal import __doc__
+    from _pydecimal import __version__
+    from _pydecimal import __libmpdec_version__
+
+if __name__ == 'PYOBJ.COM':
+    import _decimal
+    BasicContext = 0
+    Clamped = 0
+    Context = 0
+    ConversionSyntax = 0
+    Decimal = 0
+    DecimalException = 0
+    DecimalTuple = 0
+    DefaultContext = 0
+    DivisionByZero = 0
+    DivisionImpossible = 0
+    DivisionUndefined = 0
+    ExtendedContext = 0
+    FloatOperation = 0
+    HAVE_THREADS = 0
+    Inexact = 0
+    InvalidContext = 0
+    InvalidOperation = 0
+    MAX_EMAX = 0
+    MAX_PREC = 0
+    MIN_EMIN = 0
+    MIN_ETINY = 0
+    Overflow = 0
+    ROUND_05UP = 0
+    ROUND_CEILING = 0
+    ROUND_DOWN = 0
+    ROUND_FLOOR = 0
+    ROUND_HALF_DOWN = 0
+    ROUND_HALF_EVEN = 0
+    ROUND_HALF_UP = 0
+    ROUND_UP = 0
+    Rounded = 0
+    Subnormal = 0
+    Underflow = 0
+    __libmpdec_version__ = 0
+    __version__ = 0
+    getcontext = 0
+    localcontext = 0
+    setcontext = 0